Numerous systems have been developed for transforming different voltage levels in the delta and wye configurations into other voltages by the use of switch arrangements on tapped primary windings of a multiphase transformer. In general, however, these devices have been very complicated, multipurpose devices. As such, they have usually included complex switching and tap changing arrangements which are expensive and can cause reliability problems.
There is currently a need to provide a voltage transformer apparatus wherein multiphase input voltages having different levels in the delta and wye configurations are converted into a multiphase constant amplitude output voltages in one of the configurations. In the particular application of interest, it is desired to transform three-phase power susceptible of having predetermined different line to neutral and line to line input voltages in the wye and delta configurations into a three-phase wye configuration having the same line to neutral output voltage for all of the predetermined input voltages. The ratios between the line to neutral input and output voltages for the wye input voltage configurations are 120:120, 220:120, 240:120. The ratio between the line to line input and line to neutral output voltages for the delta configuration are 240:120 and 200:120. It is necessary for the apparatus to be as inexpensive as possible and to be highly reliable. As such, it is desirable for there to be constant connections between the secondary windings and the multiphase wye connected output terminals.
It is, accordingly, an object of the present invention to provide a new and improved voltage transformation apparatus wherein multiple predetermined input voltages in the delta and wye configurations are transformed into a multiphase output having a predetermined voltage for each phase, in one of said configurations.
Another object of the invention is to provide a new and improved voltage transformation apparatus for converting plural multiphase input voltages having different predetermined levels in either the delta or wye configuration into an output voltage having a predetermined value in one of the configurations, wherein the transformation apparatus is highly reliable and relatively inexpensive.
Still another object of the invention is to provide a new and improved multiphase transformer apparatus for converting multiple voltages in the delta or wye configuration into a multiphase wye output having a constant phase to neutral voltage level, wherein transformer secondary winding circuitry is maintained the same regardless of the input, thereby to improve reliability and economy.
Still another object of the invention is to provide an apparatus for inexpensively and reliably transforming wye line to neutral voltage levels in accordance with input-output of ratios 120:120, 220:120, 240:120 and for converting delta line to line voltages into a wye line to neutral voltage in accordance with the ratios 240:120 and 200:120.